So this is an idea, you have to run through dead space, you can collect artifacts and such which adds time to the other persons finish time, any time one of you get scared (either by jump scare or just being freaked out) you add time to your end score. The one with the best time wins!
Also forgot something here, they would have to do all of the optional quest included the co-op, and for that they would be allowed a person of their choosing to have them play it with. (dont know if they should be carver or not, due to the fact that carver's view is scarier than isaac's)
And deaths give them a 20 mins added to their total time at the end.* (*Partners wouldn't count, but they would have to redo a segment)